Final answer:
The equilibrium frequency of deleterious alleles will be low under strong selection and low mutation rates, and higher when selection is weak and mutation rate is high.
Step-by-step explanation:
According to the basic model of mutation/selection balance, if selection is strong and the mutation rate is low, the equilibrium frequency of the deleterious alleles will be low. This is because strong selection will swiftly eliminate deleterious alleles from the gene pool.
Conversely, when selection is weak and the mutation rate is high, the frequency of the allele will be higher, as the alleles are not being effectively selected against and mutations continue to introduce new deleterious alleles into the population.